H C Pereira - Policy and Practice in the Management of Tropical Watersheds

Winrock Development-Oriented Literature Series
Steven A. Breth, series editor

Policy and Practice in the Management of Tropical Watersheds was prepared under the auspices of Winrock International Institute for Agricultural Development.

ALSO IN THIS SERIES

Rice in the Tropics: A Guide to the Development of National Programs, Robert F. Chandler, Jr.

Small Farm Development: Understanding and Improving Farming Systems in the Humid Tropics, Richard R. Harwood

Successful Seed Programs: A Planning and Management Guide, Johnson E. Douglas

Tomatoes in the Tropics, Ruben L. Villareal

Wheat in the Third World, Haldore Hanson, Norman E. Borlaug, and R. Glenn Anderson

Cassava: New Potential for a Neglected Crop, James H. Cock

Potatoes: Production, Marketing, and Programs for Developing Countries, Douglas Horton

H. C. Pereira
with illustrations by the author

First published 1989 by Westview Press

Published 2019 by Routledge
52 Vanderbilt Avenue, New York, NY 10017
2 Park Square, Milton Park, Abingdon, Oxon OX14 4RN

Routledge is an imprint of the Taylor & Francis Group, an informa business

Copyright 1989 by Winrock International

All rights reserved. No part of this book may be reprinted or reproduced or utilised in any form or by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying and recording, or in any information storage or retrieval system, without permission in writing from the publishers.

Notice:
Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe.

Library of Congress Cataloging-in-Publication Data
Pereira, H. C. (Herbert Charles), 1913
Policy and practice in the management of tropical
watersheds.
(Winrock development-oriented literature series)
Bibliography: p.
Includes index.
1. Watershed managementTropics. 2. Agriculture
Tropics. I. Title. II. Series.
TC526.5.P47 1989 333.91'15'0913 88-33794

ISBN 13: 978-0-367-28317-9 (hbk)

I thank Dr. K.G. Tejwani, former director of the Central Soil and Water Conservation Research and Training Institute, Dehra Dun, India, for helpful discussions in the planning of this book.

Photographs and figures are by the author except as otherwise indicated.

Sir Charles Pereira FRS

Misuse of land on tropical watersheds in developing countries is increasing rapidly in association with accelerating population growth and the accompanying poverty. Destruction of natural vegetation without replacement by productive agriculture or forestry imposes severe penalties of soil erosion and sediment transport. Sedimentation destroys reservoir storage capacity and inhibits investment in power generation and irrigation.

Tropical meteorological events create seasonal water surpluses that produce floods in the lowlands. Flood abatement requires construction of storage structures in addition to good land use: only storage dams can both regulate flows and harvest the energy from them. Watershed management for stable conditions of vegetation, soils, and water is a critical requirement for investment in such flood protection.

Every corrective step to arrest watershed degradation improves the welfare of the inhabitants, both rural and urban:

Technologies of soil conservation are well known but are durable only if the standard of farming is also improved. Productivity of crops and the stability of soils improve together.

In this book, the upper watershed technologies are described in plain language and successful examples are quoted. Where it has been possible to assess costs and benefits examples are quoted.

In the lowland reaches of tropical and subtropical river basins, the critical deficiencies are in the provision and maintenance of drainage. Salinity is the penalty for waterlogging: it denies to the third world the use of much of the great arid alluvial plains that could be irrigated by the Upper Ganges, Indus, Euphrates, Tigris, and Nile.

Distribution of water from irrigation canals between farms and within farms has been neglected as an aspect of management so that severe water losses and waterlogging occur widely. Successful solutions are described.

National, international, bilateral, and non-government agencies are making important contributions to the correction of watershed misuse, but are not coordinated either by country or by watershed. The national governments of tropical developing countries are not yet giving priority to rural area development in spite of growing food shortages. The primary cause of the watershed resource destruction in the tropical world has been rapid growth of population, which has overwhelmed government machinery for rural development and the management of natural resources. There is much confusion of emotion with moral judgment of this issue. No assumptions need be made, or should be made about the ultimate size of the population of any country. It is, however, an inescapable concern of common humanity that the arrival of extra millions of children should be delayed until arrangements can be made to feed them. In the meantime, irrevocable losses of soil, of water resources, and of reservoir sites reduce the agricultural and forestry production needed for the maintenance of growing populations. The race against time is being lost in Africa and is being narrowly held in Asia and South America.

Sir Charles Pereira FRS

Policy and Practice in the Management of Tropical Watersheds

Before discussing policies of watershed management and the evidence for their consequences, it is appropriate to summarize the reasons why the fate of watersheds in the tropics) These reports showed collectively that the world food problem is concentrated in the broad belt of tropical and subtropical developing countries. Unless major efforts are mounted on an unprecedented scale to improve land use and the productivity of agriculture and forestry in these countries, their poverty and scarcities of food, water, and fuel will increase to disaster levels.

At the same time, the low yields of tropical subsistence farming present a great opportunity for improvement. The protection and management of soil and water resources are the critical factors for success. In 1984 world grain production reached a record level in the high latitudes with an embarrassing 20 percent surplus for storage, yet the third successive year of drought has accelerated the time scale of agricultural decline for most of the African continent so that major food problems are already with us. The world total of grain production has little relevance to food shortages in the tropics; severe economic and logistic constraints prevent the continuous mass transfer of food from the higher latitudes from being a sustainable solution.